Contact construction



July 19, 1949. s. MILLER Erm.

CONTACT CONSTRUCTION Filed May 29, 1943 Fly a.

INVENTORS Szepbafn Mller Pele rA. Ponft'us. B21/ ATrORN Patented July19, 19,49L y I ww tins, East Pittsburgh, Pa.,

rs to Weltinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application May 29, 1943, Serial No. 488.980

1 Claim. (Cl. 173-324) This invention relates, in general, to electricalcontact structures, and more specifically to resilient contactstructures. There are many applications where electrical contactstructures having resilient characteristics are required. In many ofthese applications, the contacts are subjected to alternate heating andcooling, and it is necessary that the resilient characteristics of thecontact remain unimpaired under such conditions in order that adequatecontact pressure be assured at all times. l

In the past, the problem has been solved by adding spring reinforcingmembers to brace contacts of a non-resilient material, such as copper.Such reinforcing members comprise extra parts added to conventionalcontacts and materially increased the complexity and cost of thecontacts. Another approach to this problem has been the use of copperalloys as contact materials. This, however, involves the use ofrelatively rare metals, and also increases the cost.

One object of this invention is to provide a novel resilient contactconstruction which is etilcient in operation yet economical ofmanufacture.

A more specic object of the invention is to provide a novel contactstructure comprising a core of resilient material at least the majorpor- 'tion of which is clad with a good electrical conducting material.

Another object of this invention is to provide a novel contactconstruction embodying a core of a material capable of heat treatment toobtain resilient properties, with at least the major portion of the coreclad with a good electrical conducting material.

Another object of this invention `is to provide a novel contactstructure comprising a core of resilient material clad with a goodelectrical conducting material, and having on at least the contactingportion thereof a layer of a noble metal.

Another object of this invention is to provide a novel contact structurebent to shape from composite strip material which is capable of heattreatment after bending to obtain resilient properties.

These and other objects of this invention will become more apparent uponconsideration of the following detailed description of preferredembodiments thereof when taken in connection with the atta/cned drawing,in which:

Figure 1 is a side elevation view of a fuse mounting having contactclips constructed in accordance with this invention;

2 tact clips constructed in accordance with this invention;

Fig. 3 is a section through one contact clip shown in Fig. 1, and takensubstantially along the line III-III thereof;

Fig. 4 is a section through a contact clip taken substantially on theline IV-IV oi Fig. 2;

Fig. 5 is an enlarged transverse section taken through one leg of theclip shown in Fig. 4 substantially on the line V-V thereof;

Fig. 6 is an enlarged transverse section taken through one leg of theclip shown in Fig. 3 substantially on the line VI-VI thereof;

Fig. '1 is an enlarged transverse section through one leg of the clip ofFig. 3 taken substantially on the line VII-VII of Fig. 3;

Fig. 8 is a section of a clip similar to Fig. 4, but illustrating amodified form; and Fig. 9 is an enlarged transverse section takenthrough one leg of the clip shown in Fig. 8.

The contact constructions constituting this invention may be embodied invarious types of electrical apparatus wherein resilient contacts arerequired. The invention is illustrated in the drawing as embodied incontact clips which must Fig. 2 is a side elevation view of a combined nfuse and disconnect switch mounting having conhave resilientcharacteristics in order to provide an adequate contact pressure when acooperating contact is inserted in the clip.

In Fig. 1, there is illustrated contact clips constructed in accordancewith this invention for cooperation with a fuse. The fuse is preferablymounted on a base 2 of insulating material, such as porcelain or amolded insulating material. Generally U-shaped contact clips l and t aresupported on the base and secured thereto by bolts 6 extending throughapertures provided in the bight portions of the clips, respectively, andthrough apertures in base 2.

In accordance with this invention, the contact clips 4 and 5 arepreferably made by cutting strips of suitable length from compositestrips, straps, flat rectangular wires or the like. These compositestrips or the like comprise a central layer or lamination I of aresilient material, preferably a material such as carbon steel which isresponsive to heat treatment to acquire increased springcharacteristics. The central layer l is clad with a relatively goodelectrical conducting matcrlal I0, such as copper, brass, silver, or thelike. Any desired method may be employed for securing the layers 8 andIl together. One method which may be employed comprises supporting asteel billet in a mold and pouring the molten copper or other goodelectrical conducting material around the steel billet to completelyenclose the 'mcnbasell Another method for making the strips from whichfuse clips may be cut, is to apply the strips oi copper or other goodconducting material to opposite sides of a steel billet, sheet or thelike. and roll the resulting sandwich-like structure at a predeterminedhigh temperature to cause the outer and inner layers to becomeintimately bonded together. Such a structure may then be rolled to thedesired thickness, and the strip of material produced will besubstantially as shown in Fig. 5, that is, the central steel layer willbe provided with good conducting material Il only on opposite sidthereof, with the edg of the steel layer exposed. This method of makingstrips from which fuse clips may be cutl will be hereinafter referred toas the rolling method.

When strips are cut from a strip or the like formed in accordance withthe casting method, they may be further cut along one edge to provideintegral tabs l2 which may then be bent inwardly towards each other toform stops. During the cutting operation, the contact clip blanks mayalso be cut to iorm an integral terminal Il which extends laterally fromthe bight portion of the clip. The contact clip I shown in Figs. 1, 3, 6and 7 is bent to shape from material formed by the casting method. Itwill be noted that this clip has conducting material Hi covering themaior portion of central layer 8, but has the central layer or core 8exposed at the outer end edges of the leg portions of the clip, and atone side edge, except for the space occupied by stops i2. This clip hasthe leg portions thereof formed with outwardly curved intermediateportions for receiving terminal ierrules I8 ons fuse Il. Stops I! formedon clips 4 and l are for the purpose of preventing longitudinal movementci the fuse relative to the clips.

After the contact clip has been bent to shape, such for example as theshape illustrated in Fig. 3, the clip may then be subjected to heattreatment to harden the steel core l and increase the resiliencythereof. Sucha treatment, while hardening the steel and increasing itsresilient characteristic. may or may not have this eiiect on the outerlayers I 0 depending upon the material used. Thus, relatively purecopper does not have any resilient properties imparted to it by heattreatment but the conductivity thereof is increased by such treatment.'Certain copper ailoys, however, such as beryllium copper, do have theixmilient properti increased by heat treatmen Pour contact clips Il, 22. uand Il are illustratedinl'lg.2asbeingsupportcdonabase2lofinsulatingmaterial, inthesamemannerascontactclipslandlarelupportedonthebase I of Pig. l. The two intermediatecontact clips u and Il are shown as having an integral com- The clipssupported on base Ii are formed with leg portions having ilat parallelintermediate portions terminating in flared outer ends for cooperationwith the knife blade terminals 2l oi' atuse 3l, and for receiving adisconnecting switch blade 32. The disconnectim twitch blade 32 may bepivotcd on clip 24, al by apivotu, formovementoitheotherendtherso( intoand out of engagement with-contact clip Il.

an added layer It applied thereto of a noble metal such as silver. gold.platinum or the like. Figs. B and 9 illustrate a contact clip like thatshown in Pig. 4 having an added coating II. Where silver is utilised forthe material for coating it, it is preferably electrolytically appliedso as to completely enclose central layer I to protect it fromcorrosion. Layer also serv the purpose of improving the contact surface,and providing a complete jacket for layers l and il of good conductingmaterial. thereby increasing the conductivity oi the clip and decreasingthe electrical contact resistance of the'clip.

Contact constructions such as those described above have a relativelyhigh electrical conductivity, and also have very good resilientcharacteristics. and these results are obtained by the economical use oirelatively common materials. Thus, steel which is a relatively cheap andabundant material constitutes the main portion of the contact, and onlya relatively small amount of copper or other good electrical conductingmaterial need be employed, as compared to contacts constructed entirelyof copper, or similar material, or alloys thereof. Moreover, by coveringsubstantially the entire surface o! central layer 8, the steel isprotected from corrosion, and by using a protective laver of relativelygood electrical conducting material, low contact resistance is obtainedand the conductivity of the clip is materially increased. As pointed outabove, the outer layer Il of good electrical conducting material maycover the entire surface of central layer 8. in which case even betterprotection oi the central layer is obtained. together with increasedconductivity. By providing a covering of good electrical conductingmaterial. at least on opposite sides of the central layer l, a terminalmay be formed integral with the contact. or may be secured to eitherside thereof in engagent with either layer Il oi good electricalconducting material. It is believed apparent that with a contact clipconstructed in accordance with this invention, no supplementalreinforcing meam is necessaryaswith solidcopperclips,becauseot the highresiliency oi central layer l. Obviously.leucopperisrequiredthanwithsolidcopper clipsorclipsoi'aoopperallcy.Furthermore. contacts constructed in accordance with this inventionmaybetirstbenttolbapaafterwhich they may be heat-treated to impartadditional resiliency to the central layer I.

Having described preferred embodiments of the invention in accordancewith `the patent statutes. it is desired that the invention be notlimited to these particular embodimentsinasmuchasitwillbeobvioustopenonsskilledintheartthatmanymodiiicationsandcbangesmay be made in these particularembodiment witboutdepartingtromthebroadspiritandscopeot this invention.

We claim as our invention:

An elongated resilient contact member constructsd to engage acooperating contact member at one point and to have an electric oductsecured thereto at a remote point, comprising, Number an elongatedcarbon steel lea! spring having rela- 537,538 tively high electricalresistance, said spring' be- 1,001,669 ing clad with a resilientberyllium copper alloy 1,025,246 in a continuous layer connecting saidpointe. 5 1,603,682 STEPHAN MILLER. 1,873,931 PETER A. PONTIUS.1,881,997 1,925,856 REFERENCES CITED 2,181,083 The following referencesare of record in the 10 23061662 le of this patent: UNITED STATESPATENTS 212711111 Number Name Date 2,281,446

471,271 Metzger Mar. 22, 1892 8 Name Date Metzger Apr. 16,' 1895 Monnot.Aug. 29, 1911 Cole May '1, 1912 Gagnon Oct. 19. 1929 Matsen Aug. 23,1932 Browne Oct. 11, 1932 Vaughan Sept. 5. 1933 Payette Nov. 21, 1939Conradi et al July 2, 1940 Staples July 9, 1940 Pierce Jan. 6, 1942lWul' Jan. 27, 1942 Laise Apr. 28, 1942

